Sleep abnormalities are co-morbid with many psychiatric conditions though whether sleep disorders are a cause or consequence of depression is unclear. A total night of sleep deprivation has immediate antidepressive actions in the clinical population, although the signaling pathway is unknown. We propose that adenosine underlies the antidepressive effects of sleep deprivation because i) adenosine regulates sleep, ii) sleep deprivation elevates adenosine, and iii) single nucleotide polymorphisms in adenosine transporters and a metabolic enzyme have been identified in patients with depression with disturbed sleep. We demonstrated that astrocytes contribute to the behavioral responses to acute sleep deprivation. We conditionally expressed the SNARE domain of a vesicle protein in astrocytes to impair exocytosis resulting in reduced extracellular adenosine, as assessed by reduced basal activation of neuronal A1 receptors (A1R), reduced slow wave activity (SWA) during non-rapid eye movement (NREM) sleep and impaired recovery sleep following sleep deprivation. We hypothesize that the antidepressive effects of acute sleep deprivation are mediated by astrocyte-derived adenosine acting on neuronal A1 receptors. Aim 1: We will test the hypothesis that astrocytic modulation of sleep homeostasis contributes to antidepressive effects of sleep deprivation. We will determine whether a total night (12h) of sleep deprivation leads to antidepressive like effects, then using dnSNARE mice will ask whether the astrocytic sleep homeostat is required to mediate depressive-like responses. Aim 2: We will test the hypothesis that A1 receptors are required to mediate the antidepressive-like effects of sleep deprivation. We will determine whether 12h of sleep deprivation leads to enhanced activation of A1R and using central delivery of A1R antagonists and A1R knockout (A{1}R[-/-]) mice we will determine whether antidepressive-like effects of sleep deprivation require A1R. Aim 3: We will test the hypothesis that sustained (12h) pharmacological activation of central A1R will produce antidepressive like effects. We will deliver A1R agonists intracerebroventricularly (i.c.v.) and wil ask whether the activation of this receptor pathway yields antidepressive like effects. Aim 4: We will determine the role of frontal cortex in contributing to antidepressive effects of sleep deprivation. We will expand preliminary c-fos immunoreactivity studies and the use of novel Tet Tag transgenic mouse that enables GFP-labeling of c-fos active neurons to identify sleep deprivation activated neurons of the frontal cortex. Finally, we will virally transduce frontal corex astrocytes with dnSNARE and ask whether region specific transduction inhibits antidepressive effects of sleep deprivation. The identification of a signaling pathway underlying antidepressive like effects of sleep deprivation has the potential to for the future development of glial-based therapeutics for the immediate relief of depression.